Fixing a warp

Something I experimented with. I HTed a couple of kitchen knives yesterday, and one developed a kink during the quench. Rather than forge it straight again and re-HT, I decided to try something different.
First I tempered it for 2 hours. Then I used a thick piece of stock, 2 pieces of scrap and a C clamp to bend that kink the other way and tempered it again for an hour and let it cool te room temp. The kink was already a lot less. A second temper cycle clamped like that, and the blade was perfectly straight.

For razors you could try something similar after the first temper cycle.

I also learned that cutting your finger on the side of a fast running 40 grit belt hurts surprisingly little. It just looks gross because it doesn't cut, it gouges. And then there was a lot of black swarf I had to clean out because my finger acted like a belt cleaner. It'll probably take a while to heal too. :(

Bruno,
Sorry to hear of the mishap and I hope you heal quick. Thanks for the information, I may try to apply this to a vintage I have in the future.

Let's get those kitchen knives on the line, Bruno,,,I've only got one lonely Combat Meat Knife by Bruno of Belgium & it has to battle a ham all by itself next week,,,,:shrug: :D

Good to know, thanks Bruno. I'll probably be making my first kitchen knife over the next couple of weeks
Grant

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Originally Posted by baldy

Good to know, thanks Bruno. I'll probably be making my first kitchen knife over the next couple of weeks
Grant

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I haven't had this problem with razors yet, because razors ar relatively thick and short.
Kitchen knives are long and thin, so much more likely to do something. Anneal at least once after you've done all the work, before you quench. That should get rid of a lot of stress. And don't grind too thin near the edge. One of my kitchen knives had a little bit of potato chip edge because it was to thin.

The nice thing of straightening blade this way is that the difficult / error prone parts are done with, and you can gently ease up to the final form.

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Originally Posted by Hirlau

Let's get those kitchen knives on the line, Bruno,,,I've only got one lonely Combat Meat Knife by Bruno of Belgium & it has to battle a ham all by itself next week,,,,:shrug: :D

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I'll send backup :p

IIRC, Bill Moran used a method like that as well.

Edit: He used clamped HOT steel on the spine to soften the spine, but keep the edge hard.

Worse part of you using your fingers to clean your belts is that it takes a bit for those type of "gouges" to heal. Keep it covered with a antibiotic ointment & band-aid & you will stay good to go.

Well when I was a kid and that sort of thing would happen, grandpa would go out to the shed and pour naptha on it. Then come in and grandma would smear bacon drippings on it. Then wrap it up!
Don't know if it made a difference or not. Grandpa died with all his digits intact. He did substitute "Old Crow" for aspirin too!!
Thanks for the thread. I was looking into making some native Alaskan 'Ulu" knives. Was wondering if there would be a problem with warpage due to the mass of metal involved.
This thread give me some relief knowing that it is possible to straighten them if they decide to head south!!
Thanks Bruno!!

Grinder cuts take forever to heal. Best of luck. Sometimes with a stubborn warp or corkscrew bend I heat the blade up in the tempering oven to tempering temperature and counter bend it hot witch gloves on or in the vise.

Or use the three pin method.

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Originally Posted by PierreR

Or use the three pin method.

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Yes, that is what I do in the vise. I have one piece of angle iron with one pin welded on and another piece with two pins. I could not think of the term. It works well but can be a bit unnerving as the steel starts to cool and you think, "just one more squeeze"

You have peeked my interest Bruno! Can you send a pic of the kitchen knife you are working on?

Ray

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Originally Posted by JMJones

Yes, that is what I do in the vise. I have one piece of angle iron with one pin welded on and another piece with two pins. I could not think of the term. It works well but can be a bit unnerving as the steel starts to cool and you think, "just one more squeeze"

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In this case I wouldn't dare, because they were irreplaceable. They are for my best friend who has always been interested in knives and in my knifemaking. He wanted to have a forged kitchen knife, but they cost too much if you want to buy them in the store. In the summer I asked him over and we forged a pair together, and the project went dormant for a while, until I got my ceramic belts 2 weeks ago and ground several knives; those 2 among them. I HTed them last week and am now polishing them. I really want to have them ready by new years eve as a surprise gift when he and his wife are coming over.

Anyway, that's why I wanted to try a straightening method with the least amount of risk. The 3 pin method might be quicker, but I was not about to risk breaking those knives I forged with help from my friend. :) I could quickly forge a new one of course, but it wouldn't be the one we made together.